With the development of a wireless communication technique, information communication terminals, such as mobile phones, PDAs, and GPS receivers, have become popular. Patch antennas having a small size, a small thickness, and light weight are generally used for the information communication terminals.
FIG. 1 is a diagram illustrating an example of a patch antenna according to the related art. Since the patch antenna shown in FIG. 1 includes a ceramic dielectric substrate, it is also called a ceramic patch antenna. The patch antenna shown in FIG. 1 includes a dielectric substrate 10 having a predetermined thickness, a planar patch that serves as an antenna and is provided on one surface (upper surface) of the dielectric substrate 10, and a ground plate 14 that is provided on the other surface (lower surface) of the dielectric substrate 10.
The patch 12 can be formed in various shapes, such as a rectangle, a circle, an ellipse, a triangle, and a ring, in plan view. The patch 12 is generally formed in a rectangular shape or a circular shape in plan view.
Power can be supplied to the patch 12 through a micro-strip line or a probe. When power is supplied through the micro-strip line, antenna characteristics and input impedance depend on the position where power is supplied. Therefore, matching between the feeding line and the patch is important, but the method of supplying power through the micro-strip line has an advantage in that it is easy to manufacture the antenna. In the method of supplying power using the probe, it is possible to supply power to a position where the feeding line and the patch are well matched with each other, and thus an additional matching circuit is not needed.
In general, the size of the patch antenna is proportional to the wavelength of a design frequency. When the same frequency is used, a dielectric substrate having a high relative dielectric constant should be used to reduce the size of the patch antenna.
However, when a dielectric material having a high relative dielectric constant is used, the radiation characteristic of the antenna is lowered, resulting in a low gain.
When the relative dielectric constant of a dielectric material increases, manufacturing costs increase, and yield is rapidly lowered. Therefore, there are limitations in using a dielectric material having a high relative dielectric constant to reduce the size of an antenna.
In order to solve these problems, Korean Patent No. 10-0562788 discloses a patch antenna.
The patch antenna disclosed in Korean Patent No. 10-0562788 includes: a patch that includes one or more corners having a ‘U’ shape or a ‘W’ shape; a ground plate that is spaced from the patch by a predetermined gap therebetween and includes one or more corners having a ‘U’ shape so as to cover the corners of the patch; and a dielectric layer that is provided between the ground plate and the patch. The patch includes a patch body having a predetermined shape in plan view and vertical and horizontal portions that are formed in a ‘U’ shape or a ‘W’ shape by bending the corners of the patch body two times. The ground plate includes a plate body having a predetermined shape in plan view, and vertical and horizontal portions that extend from the edge of the plate body and are bent. The horizontal portion of the ground plate is opposite to the plate body with the patch interposed therebetween.
In the folded patch antenna disclosed in Korean Patent No. 10-0562788, when the dielectric layer is used as an air layer, it is possible to simplify a manufacturing process. However, when a dielectric material having a high relative dielectric constant is used instead of the air layer in order to reduce the size of an antenna, the manufacturing process becomes complicated.
In order to solve this problem, a patch antenna (Korean Patent No. 10-0562786) using a dielectric layer laminating process has been proposed.
The patch antenna disclosed in Korean Patent No. 10-0562786 includes: a ground plate; a patch that is spaced from the ground plate by a predetermined gap therebetween; a dielectric layer that is provided between the ground plate and the patch; and a plurality of protrusions that have a predetermined height and are arranged at predetermined intervals on the patch and/or the ground plate.
In the patch antenna disclosed in Korean Patent No. 10-0562786, as shown in FIG. 2, thin dielectric films 50 are laminated. A patch 20 is printed (coated) on the uppermost dielectric film 50. A plurality of holes 54 are formed in the dielectric film 50 having the patch 20 printed thereon and the other dielectric films 50 in a predetermined pattern, and the dielectric film 50 having a predetermined thickness is laminated thereon. Then, a conductive material is filled into the holes 54, and is heated so as to be melted, thereby forming a plurality of protrusions. In FIG. 2, reference numeral 22 denotes a ground plate, reference numeral 56 denotes a hole for supplying power.